There are many medical situations presented where it is highly desirable, if not absolutely essential, for the attending physician to have data as to the patient's electrical heartbeat activity in order to make a sound medical judgment. The usual situation is one where the symptoms of a patient do not warrant hospitalization and yet require the generation of electrical heart activity data upon which the physician can make a sound medical judgment. Of course, where the patient is in a coronary care unit expensive and complex equipment can be provided to supply any and all required data. There are, however, additional hospital related situations where such data is useful and necessary as, for example, when the patient is beginning to move out of the coronary care unit within the hospital and then out of the hospital as an out-patient. In order to supply the required data in these situations beyond intensive coronary care, so-called "Holter" ambulatory monitors have been developed (e.g. U.S. Pat. No. 4,211,238). Originally devices of this type provided the simple capacity of recording in real time the electrical heart activity of a patient carrying or wearing the device for a 24 hour period.
The usual situation was for a physician to order the so-called Holter test requiring the patient to come into a facility where the operation of the device could be demonstrated and an initial connection to the patient could be affected. In conjunction with the operation of the device the patient was given a diary within which to record on a time basis activities during the 24 hour monitoring period as well as any symptomatic events which may occur. Many of the devices were provided with means by which the symptomatic events could be signaled in the tape by the patient pressing a button or the like. The usual procedure after monitoring had been completed required the patient then to come back to the facility and to disconnect the monitor so that the recorded data could then be processed for use by the attending physician.
Clearly it is impractical for a physician to have to spend 24 hours playing back the tape in order to assimilate the data represented by the same. Consequently, machines were developed for analyzing the tapes. The machines developed for this purpose (e.g. U.S. Pat. No. 4,073,011) all required manual operators who, by visual inspection of an oscilloscope or equivalent, made judgments such as abnormal cardiac activity as to which portions of the recording should be printed out as rhythm strips. Because of the operator judgment factor, the usual situation was to centralize the location of the processing machines so that skilled operators could be efficiently employed on a continuous basis. Consequently, while the practice of some doctors may be sufficiently specialized as to provide a volume sufficient to justify a full-time operator, the more prevalent method of operating was to centralize the operation to a point requiring that the recorded data be sent from the location where the monitor was connected and disconnected to a remote location which in many instances could be from a doctors office to a larger facility in a hospital or big city. Other alternatives included the setting aside of facilities in a hospital to perform both the connection and disconnection procedures as well as the data processing procedures.
In any event, in order to facilitate the data processing, the machines involved were developed so as to enable the tapes to be operated at ever increasing speeds. In the early machines speeds of the order of 60 times real time were utilized, whereas the more sophisticated and modern machines have operated at speeds of up to 480 times real time. It is generally accepted, however, that as speeds increased accuracy and/or consistency tended to decrease.
In order to recapture the lost accuracy of high speed processing, the monitors of more recent vintage have embodied therein the capability of analyzing the electrical EKG captured on a real time basis as it is being captured. (See, for example a paper entitled "Real Time Analysis of Holter ECG Data Represents a Major Technological Advance" by Norman H. Holter published in the Holter Research Foundation, Inc.) Further, these monitors were provided with the capability of selectively recording rhythm strips based upon the analyzation or real time processing being carried out. The use of these processing monitors seemed to offer a simplification of the subsequent processing required. However, the normal operating mode remained unchanged and there was subsequent processing required which, as before, was carried out at central locations with the attendant patient inconvenience and delays occasioned as a result of transportation time and scheduling of machine time.
While these recently proposed real time processing ambulatory monitors appear to offer the prospect of recapturing the lost accuracy associated with high speed machine processing and reducing to some extent the processing delays heretofore experienced, there still exists the need to further reduce these delays and to alleviate the patient inconveniences associated therewith.